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901.
Survival rates of juvenile reptiles are critical population parameters but are difficult to obtain through mark-recapture programs because these small, secretive animals are rarely caught. This scarcity has encouraged speculation that survival rates of juveniles are very low, and we test this prediction by estimating juvenile survival rates indirectly. A simple mathematical model calculates the annual juvenile survival rate needed to maintain a stable population size, using published data on adult survival rates, reproductive output, and ages at maturity in 109 reptile populations encompassing 57 species. Counter to prediction, estimated juvenile survival rates were relatively high (on average, only about 13% less than those of conspecific adults) and highly correlated with adult survival rates. Overall, survival rates during both juvenile and adult life were higher in turtles than in snakes, and higher in snakes than in lizards. As predicted from life history theory, rates of juvenile survival were higher in species that produce large offspring, and higher in viviparous squamates than in oviparous species. Our analyses challenge the widely held belief that juvenile reptiles have low rates of annual survival and suggest instead that sampling problems and the elusive biology of juvenile reptiles have misled researchers in this respect. 相似文献
902.
Invisible floral larcenies: microbial communities degrade floral nectar of bumble bee-pollinated plants 总被引:2,自引:0,他引:2
The ecology of nectarivorous microbial communities remains virtually unknown, which precludes elucidating whether these organisms play some role in plant-pollinator mutualisms beyond minor commensalism. We simultaneously assessed microbial abundance and nectar composition at the individual nectary level in flowers of three southern Spanish bumble bee-pollinated plants (Helleborus foetidus, Aquilegia vulgaris, and Aquilegia pyrenaica cazorlensis). Yeasts were frequent and abundant in nectar of all species, and variation in yeast density was correlated with drastic changes in nectar sugar concentration and composition. Yeast communities built up in nectar from early to late floral stages, at which time all nectaries contained yeasts, often at densities between 10(4) and 10(5) cells/mm3. Total sugar concentration and percentage sucrose declined, and percentage fructose increased, with increasing density of yeast cells in nectar. Among-nectary variation in microbial density accounted for 65% (H. foetidus and A. vulgaris) and 35% (A. p. cazorlensis) of intraspecific variance in nectar sugar composition, and 60% (H. foetidus) and 38% (A. vulgaris) of variance in nectar concentration. Our results provide compelling evidence that nectar microbial communities can have detrimental effects on plants and/or pollinators via extensive nectar degradation and also call for a more careful interpretation of nectar traits in the future, if uncontrolled for yeasts. 相似文献
903.
Among pelagic fish, the Southwestern Atlantic menhaden genus Brevoortia (Clupeidae, Alosinae) constitutes an important species model to investigate the patterns of genetic differentiation. It is
abundant in the Río de la Plata estuary and in the Atlantic coastal lagoons system from Uruguay and Southern Brazil. To access
in the taxa discrimination and population structure in Brevoortia we perform a phylogeographic approach based on mitochondrial cytochrome b (cyt-b) sequences including 240 individuals from 16 collecting sites. Among the 720 bp cyt-b sequenced, 199 correspond to variables and 88 to phylogenetically informative sites. High values of haplotype diversity (h = 1.000) and nucleotide diversity (π = 0.061), as well as an average of 0.084 polymorphic segregating sites and 46 different haplotypes were found. Maximum likelihood
analysis based on the GTR + I + G model and Bayesian inference strongly support the idea that B. aurea is the only species of the genus inhabiting the Southwestern Atlantic region. Our analyses revealed a complex population
pattern characterized by the existence of long-term highly structured genetic assemblages of mixed stocks. Each monophyletic
entity included individuals from different collecting sites, different age groups and collected in different years. Our data
also suggest that the recruitment of unrelated mtDNA haplotypes carried out by individuals within schools could be occurring
in the same nursery areas revealing the existence of many different maternal lineages. A scenario where different simultaneously
and successively mixed mtDNA lineages remain historically connected through basal haplotypes among different clades could
explains more accurately the complex and ordered metapopulation dynamic found in this pelagic fish. 相似文献
904.
Gilad Heinisch Aldo Corriero Antonio Medina Francisco J. Abascal Jose-Miguel de la Serna Robert Vassallo-Agius Antonio Belmonte Ríos Antonio García Fernando de la Gándara Christian Fauvel Christopher R. Bridges Constantinos C. Mylonas Saadet F. Karakulak Isik Oray Gregorio De Metrio Hanna Rosenfeld Hillel Gordin 《Marine Biology》2008,154(4):623-630
Atlantic bluefin tuna (BFT; Thunnus thynnus) is a migrating species straddling the North Atlantic Ocean and Mediterranean Sea. It is assumed that this species is divided
into a western and an eastern stock, which spawn in the Gulf of Mexico and the Mediterranean Sea, respectively. To learn more
about the reproductive behavior of the eastern BFT stock, we tracked gonadal development in adult fish that were sampled between
April and July during three consecutive years (2003–2005). Sampling campaigns were carried out using common fishing methods
at selected locations within the Mediterranean Sea, namely Levantine Sea, Malta, and Balearic Islands. An additional sampling
point, Barbate, was situated northwest of the Straits of Gibraltar along the Atlantic coast. Morphometric parameters such
as the total body mass (M
B) and the weights of the gonads (M
G) were recorded, and the respective gonadosomatic index (GSI) values were calculated. The data collected revealed two important
trends: (1) GSI values are higher in fish caught in the eastern rather than the western locations across the Mediterranean
Sea, and (2) the GSI reaches maximum values between late May and early June in Levantine Sea (eastern Mediterranean Sea),
and only 2 and 4 weeks later in the central (Malta) and western (Balearic Islands) locations, respectively. The advanced gonadal
development in BFT correlates well with higher sea surface temperatures. Our findings also distinguish the northern Levantine
Sea BFT population (mean M
B 78.41 ± 4.13 kg), and the Barbate BFT population with the greatest M
B (all fish sampled > 100 kg). These data reflect a situation in which the eastern Mediterranean basin may function as a habitat
for young BFT, until they gain a larger M
B and are able to move to the Atlantic Ocean. However, the existence of genetically discrete BFT populations in the Mediterranean
Sea cannot be ruled out. 相似文献
905.
Pedro Daleo Tomás Luppi Agustina Mendez Casariego Mauricio Escapa Pablo Ribeiro Paola Silva Oscar Iribarne 《Marine Biology》2009,156(3):269-275
Size advantage in male–male competition over mates, combined with male preference over large females, is a common feature
that can drive to size assortative mating and, eventually, sexual selection. In crabs, appendage autotomy can affect assortative
mating and opportunity for sexual selection by affecting size advantage in mating contests. In this work, we evaluate the
effect of size and appendage autotomy in generating assortative mating in the mud crab Cyrtograpsus angulatus. Field observations of guarding pairs in two different populations show a positive correlation between carapace width of
males and females in both the populations. In one of the populations, incidence of appendage autotomy was low and the variability
in the size of reproductive males was lower than the variability in the size of randomly collected males (i.e. only larger
males were successful in getting a female), whereas there was no differences in the other population (i.e. most male sizes
were successful) where the incidence of appendage autotomy was very high, indicating that the importance of size is higher
when the incidence of autotomy is low. In this context, experiments (in both populations) show that, in contests for a female,
larger males outcompete smaller ones only when they had intact appendages. When males had missing chelipeds, winning or loosing
against smaller males was random. This may lead to a decrease in the importance of male size in populations with high incidence
of cheliped autotomy, affecting assortative mating and opportunity for selection and, thus, affecting selective pressures. 相似文献
906.
(Z)-Dodec-3-en-1-ol has been identified as the major component of the trail-following pheromone of nine species of Kalotermitidae
belonging to six different genera, suggesting that this compound represents a common signal in this family of termites. The
homogeneous nature of trail-following pheromones of Kalotermitidae well agrees with the monophyly of this family. It also
supports the postulated position of this family as a sister group of the Rhinotermitidae and Termitidae, which also secrete
C12-alcohols as trail-following pheromones. The significance of a trail pheromone in termites of the ‘one-piece’ life type,
which spend their whole life within the same piece of wood, is discussed. 相似文献
907.
de Guzmán Báez A Villoria Sáez P del Río Merino M García Navarro J 《Waste management (New York, N.Y.)》2012,32(5):920-924
In the last years, the European Union (EU) has been focused on the reduction of construction and demolition (C&D) waste. Specifically, in 2006, Spain generated roughly 47million tons of C&D waste, of which only 13.6% was recycled. This situation has lead to the drawing up of many regulations on C&D waste during the past years forcing EU countries to include new measures for waste prevention and recycling. Among these measures, the mandatory obligation to quantify the C&D waste expected to be originated during a construction project is mandated. However, limited data is available on civil engineering projects. Therefore, the aim of this research study is to improve C&D waste management in railway projects, by developing a model for C&D waste quantification. For this purpose, we develop two equations which estimate in advance the amount, both in weight and volume, of the C&D waste likely to be generated in railway construction projects, including the category of C&D waste generated for the entire project. 相似文献
908.
Correlation analysis between sulphate content and leaching of sulphates in recycled aggregates from construction and demolition wastes 总被引:1,自引:0,他引:1
Barbudo A Galvín AP Agrela F Ayuso J Jiménez JR 《Waste management (New York, N.Y.)》2012,32(6):1229-1235
In some recycled aggregates applications, such as component of new concrete or roads, the total content of soluble sulphates should be measured and controlled. Restrictions are usually motivated by the resistance or stability of the new structure, and in most cases, structural concerns can be remedied by the use of techniques such as sulphur-resistant cements. However, environmental risk assessment from recycling and reuse construction products is often forgotten. The purpose of this study is to analyse the content of soluble sulphate on eleven recycled aggregates and six samples prepared in laboratory by the addition of different gypsum percentages. As points of reference, two natural aggregates were tested. An analysis of the content of the leachable amount of heavy metals regulated by European regulation was included. As a result, the correlation between solubility and leachability data allow suggest a limiting gypsum amount of 4.4% on recycled aggregates. This limit satisfies EU Landfill Directive criteria, which is currently used as reference by public Spanish Government for recycled aggregates in construction works. 相似文献
909.
J M López-Gutiérrez M García-León C Schnabel M Suter H A Synal S Szidat 《Journal of environmental radioactivity》2001,55(3):269-282
Iodine-129 (T1/2 = 1.57 x 10(7) yr) concentrations have been determined by accelerator mass spectrometry in rainwater samples taken at Seville (southwestern Spain) in 1996 and 1997. This technique allows a reduction in the detection limits for this radionuclide in comparison to radiometric counting and other mass spectrometric methods such as ICP-MS. Typical 129I concentrations range from 4.7 x 10(7) 129I atoms/l (19.2%) to 4.97 x 10(9) 129I atoms/l (5.9%), while 129I depositions are normally in the order of 10(8)-10(10) atoms/m2d. These values agree well with other results obtained for recent rainwater samples collected in Europe. Apart from these, the relationship between 129I deposition and some atmospheric factors has been analyzed, showing the importance of the precipitation rate and the concentration of suspended matter in it. 相似文献
910.
Extractable atrazine and its metabolites (hydroxyatrazine, deethylatrazine and deisopropylatrazine) were evaluated in agricultural
soils from the temperate humid zone (Galicia, NW Spain) under laboratory conditions. The experiment was performed with five
soils with different properties (organic C, soil texture and atrazine application history), both unamended and treated with
atrazine at field application rate. Measurements of the atrazine compounds were made at different time intervals (1, 3, 6,
9 and 12 weeks) during a 3-month incubation period. Results showed that only hydroxyatrazine was detected in the extractable
fraction of the unamended soils, with values remaining relatively constant throughout the incubation period. Atrazine addition
notably increased the concentration of the parent compound and its degradation products; deisopropylatrazine and hydroxyatrazine
were the main metabolites detected in the extractable fraction of the treated soils, whereas deethylatrazine was not detected.
After 7 days incubation, values of total extractable residues, expressed as percentage of initially added atrazine, ranged
from 75 to 86% (25–68% of atrazine, 7–11% of hydroxyatrazine and 9–57% of deisopropylatrazine). The values decreased rapidly
during the first 3 weeks of incubation, showing values of 2–8% in soils with higher atrazine application and from 28 to 30%
in soils with lower application history. At the end of the incubation, 2–8% of total extractable residues were still detected
(0–4% of atrazine, 2–3% of hydroxyatrazine and 0–2% of deisopropylatrazine), indicating a residual effect of atrazine addition.
These variations in the extractable fraction indicated that most added atrazine was rapidly degraded, especially in soils
with higher application history. 相似文献